Electrical motor pump or compressor



Aug. 28, 1956 H. H. M ADAM 2,

ELECTRICAL MOTOR PUMP OR COMPRESSOR Filed March 29, 1952 3 Sheets-Sheet 1 I INVENTOR. H4 RR) h. MLADAM ATTORNEY Aug. 28, 1956 H. H. MOADAM 2,761,078

Filed M8.I Ch 29, 19 52 ELECTRICAL MOTOR PUMP OR COMPRESSOR s Sheeis-Sheet 2 INVENTOR. HARRY H. M04044! wmw ATTORNEY Aug. 28, 1956 H. H. MCADAM 2,761,078

ELECTRICAL MOTOR PUMP 0R COMPRESSOR Filed March 29, 1952 3 Sheets-Sheet 3 INVENTOR. HARRY H. MCADAM WMM h ATTORNEY United $tates Patent ELECTRICAL MQTUR PUMP R CONIPRESSOR Harry H. McAdam, San Quins, alif., assignor to Wetmore Hodges, doing business as Wetniore Hodges and Associates, Redwood City, California Application March 29, 1952, Serial No. 279,392 17 Claims. (Cl. 310-67) This invention relates to an improved motor-pump or compressor. More particularly it relates to a motorpump in which the stator and a pair of end plates constitute the pressure vessel within which are all the other components of the motor-pump.

This invention solves many problems which have long confronted the pump and compressor industry, particularly in relation to such applications as compressors for domestic refrigerators, freezers, and air conditioners, Water coolers, and other refrigerated devices.

Three interrelated problems have been particularly troublesome and the present invention solves them: (1) how to make small enough, light enough, and inexpensive enough motor-compressors having the requisite capacity, ('2) how to improve the dissipation of the heat which the motor and compressor builds up, and (3) how to provide a pressure-tight motor-compressor, without having to encase the whole within an all-enclosing, pressure-retaining shell. A brief discussion of these three important problems will aid in understanding the present invention and its importance.

Small powerful motor-compressors have long been sought after, because space is always at a premium. Every cubic inch of space taken up by the power unit subtracts from the cabinet space that can be made available to the consumer. Moreover, large, heavy compressors have been expensive to build, ship, and store.

Their large size was one objection to the old style of compressors, which used belts and in which the motor and the compressor were separately housed. Another objection to this two-unit style of compressor was that it required shaft seals for retaining the charge of refrigerant. These shaft seals were subject to leaks, squeaks and chattering noises, which could not be tolerated. Also, these seals wore out rather rapidly and had to be replaced often.

Confronted by this problem, the industry eliminated the shaft seals by enclosing both the motor and the compressor in a single pressure-tight housing, which was usually an outer shell surrounding the whole motor-pump unit.

This brings us to the problem of heat-dissipation. An outer shellaround a motor retards the passage of the heat off into the air. The more the motor is exposed to the air, where a cooling current can be passed directly over the hot parts, the cooler the motor can be kept. Enclosure of the motor-compressor in an outer shell interferes with and seriously retards the heat flow, thereby tending to keep the heat in, resulting in undesirably high operating temperatures.

The motor heat dissipation problem was made worse by the fact that the copper wire windings of the stator did not make good thermal contact with the slots through which they pass. Dissipation of the heat which built up through electrical resistance heating of the copper wire coil bundles, depended largely on transferring this heat to the motor laminations and thence through the enclosing shell to surrounding air, and this transfer had to be made by conduction through air or refrigerant vapor, which are very poor conductors.

The above factors caused the dissipation of heat to be a more serious problem than is usually realized. Since electrical conductivity is a function of the temperature of the conductor, with electrical resistance increasing with temperature rise, it becomes evident that a cool motor can and will deliver more power than a hot motor. About the only thing that could be done with a shell-enclosed motorcompressor was to increase the size of motor and the shell, to compensate for the power lost through overheating, or to add cooling fins to the casing for the same reason. These solutions, however, conflicted directly with the problem of the keeping the size, cost, and weight of the compressor small.

In this invention, a solid fill of plastic surrounds the wire bundles and totally fills all the slot voids, providing a solid, unbroken thermal path along which the wire heat is passed directly to the stator iron stack. This solid plastic till is an appreciably better heat conductor than air or vapor. Also, since no shell encloses the stator, this heat is transferred directly to the surrounding air which is in direct contact with the outer surfaces of the laminations.

For obvious reasons, many engineers sought some way of making a pressure vessel without enclosing the motorpump in a shell. None of these attempts were successful until the present invention. One such attempt that failed, interposed a sealing element in the air gap or clearance between the stator and the rotor of the electric motorpump. This approach to the problem is exemplified by Cantons Patents Nos. 1,780,337, 1,780,338, 1,780,339 and 1,849,222. The trouble with this approach was that it introduced an even more serious problem. In an electric motor the air gap (as the clearance between the stator and the rotor is usually called) should be kept as small as possible while providing the clearance necessary for the rotor to turn. The magnetic forces between the. stator and rotor are the motive forces that drive the motor, and these magnetic forces decrease greatly with any increase in the air gap, the decrease in force being disproportionally greater than the increase in the spacing or air gap. Normally, magnetic force decreases according to the square of the distance between the parts, and even though this law may not be strictly obeyed in the air gap between the stator and the rotor, due to other forces present, any increase in the air gap does cause a disproportionate falling off in the magnetic force available to run the motor. That is why Cantons interposition of a sealing member in the air gap was a failure. No way was known of making a satisfactory pressure vessel out of the motor-compressor unit without an enclosing shell.

The present invention has solved these, three important.

related problems-how to' keep the unit small in size, light in Weight, and low in cost; how to dissipate the heat built up inside it; and how to do these and still have a satisfactory pressure vessel-by a novel structure in which a pressure vessel is made from the hollow motor stator and from two. end plates and in which all the pumping elements are inside the motor rotor. It does this without in any Way increasing the air gap between the stator and the rotor. In fact, this invention makes it possible to use an unprecedentedly small air gap.

The motor pump or compressor of this invention also solves another important problem; namely, that of pumping or compressing fluids which are corrosive or which break down into components that tend to damage or dissolve the wire windings or their insulation. This. present invention solves this problem by isolating the wires and their insulation and sealing them oil? from whatever fluid is being pumped or compressed, and the protecting substance is one which is not attacked by the fluids used in refrigeration nor by most other fiuids.

The same isolation of the stator parts acts to eliminate or isolate any entrapped or occluded water vapor and prevent it from damaging the system.

The present invention is a motor-pump or compressor that includes a hollow stator whose laminations and wire coils are encased in and sealed together by a sealant material. The stator cavity is closed at both ends by a pair of end plates, at least one of which is ported, so that the motor-pump is provided with its intake and discharge openings. The end plates may be permanently sealed to the stator by a suitable sealant or they may be removably sealed by a gasket means. In either event, the stator and the end plates constitute the pressure vessel-- without any additional shell being necessary. At the same time, the sealant is so applied that there is no foreign material in the air gap, and so that heat dissipation is improved.

Within this pressure vessel are all the components of the motor-pump, including the motor-rotor and the pumping elements. So far as the present invention is concerned, many different types of pump elements may be used. One type is illustrated in the drawings and is described by way of example, this type being the motorpump which is further described and is claimed in my copending application, Serial No. 292,140, filed June 6, 1952. However, an internal gear pump, such as the Model L pumps manufactured by the Tuthill Pump Company could be used, as well as certain of the types of pumps described by Myron P. Hill in a series of United States patents issued since 1927. Still other types of pumping elements are usable in my improved pressure vessel, as will appear to those skilled in the art after they have studied the following description.

Still other objects and advantages of the invention will appear from the following description of a preferred embodiment thereof. It will be obvious that changes in detail may be made, because this description is given by way of example in order to comply with the requirements of the U. S. Revised Statutes, section 4888. The invention is not intended to be limited to the details described, its scope being indicated by the appended claims.

In the drawings:

Fig. 1 is a reduced view in perspective of a motorpurnp or compressor embodying the principles of this invention. The connection of one of the conduits is indicated in dotted lines and the electrical connections are shown diagrammatically to prevent the face of the pump from being covered up.

Fig. 2 is a view in section showing the motor-pump of this invention, the section taken along the line 22 in Fig. 3.

Fig. 3 is a view in section taken along the line 3-3 of Fig. 2.

Fig. 4 is a view in section of the rotor of Fig. 3 and its contained parts, looking in the opposite direction and with the pump gears shown rotated through a relatively small angle.

Fig. 5 is a view in end elevation of one form of the end plates, showing an end plate having an intake port.

Fig. 6 is a view in section taken along the line 6-6 in Fig. 5.

Fig. 7 is a view in end elevation of a modified form of end plate, showing an end plate having a discharge port.

Fig. 8 is a view in section taken along the line 8--3 in Fig. 7.

Fig. 9 is a view in end elevation of a single end plate containing both an intake port and a discharge port.

Fig. 10 is a view in perspective of the electrical connection for the stator.

The electric motor-pump 10 includes a hollow stator 11 closed at each end by end plates 12 and 13. The stator 11 and the plates 12 and 13 are impervious to fluid under pressure, and they cooperate to form a fluid-tight pressure vessel, within the cavity 14 of which are all the component parts of the motor-pump 10, including a rotor 15 and the pump elements, which are preferably located inside the rotor 15. Preferably, an intake port 16 is provided in one end plate 1.2 and a discharge opening 17 is provided in the other end plate 13, although both ports may be provided in the same end plate (see Fig. 9).

The stator 11 The stator 11 may be made up of a plurality of thin iron laminations 20 secured together by a suitable thermosetting plastic or some other sealant material 21. In the drawings the thickness of the sealant layers 21 has had to be exaggerated, but in reality the laminations 20 are just as close togeth r as in any other stator, the plastic film being very thin. The sealant 21 may be put on by dip, spray, or film application to the individual laminations 20 prior to their stacking, or the sealant 21 may be forced under pressure to enter between the laminations 20 and seal their interfaces after the stack has been assembled. (For methods of applying the plastic, reference may be had to my co-pending application, Serial No. 286,880, filed May 9, 1952, now Patent Number 2,693,313.

This sealed stack is pressure tight, but its inner and outer peripheries are preferably not coated. It is important that none of the sealant material 21 be allowed to protrude out into the stator bore 22, so that the clearance area 23 between the stator and the rotor 15 remains unchanged and unobstructed by the application of the sealant 21. For one thing, a layer of plastic, coating the stator bore 22 would perforce increase the air gap or clearance area 23, thereby decreasing disproportionately the electromotive force flowing between the stator 11 and rotor 15, as disclosed earlier. The stator bore 22 is preferably perfectly smooth, although it is in effect made up of alternate layers of the metal laminations 20 and the plastic material 21 therebetween. The plastic 21 is not allowed to project even the slightest distance beyond the metal 20 because any roughness or protrusions tend to obstruct rotor-to-stator clearance and seriously interfere with the movement of a fluid film normally present between the static stator wall and the rotating rotor wall. This film is subjected to the shearing action caused by the rotative forces created by the rotor 15 turning in the stator bore 22. Any roughness or protrusions into the clearance area 23 tends to set up additional retarding forces. Therefore, it becomes apparent that extreme smoothness and uniformity are of the utmost importance.

The stator 11 is provided with a suitable number of wire slots 24 to receive suitable wire windings 25 and 26, the main windings 25 preferably being augmented by starting windings 26 which, if desired, may also remain in the circuit after starting. All the windings 25 and 26 pass through the stator slots 24 and protrude at 27 beyond the iron stack ends 28, 29, as shown in Fig. 2. These windings 25, 26 are completely imbedded in and encased by a suitable thermosetting plastic 30 or other suitable material both in the slots 24 and where the wires protrude. The encasing material 30 may be the same as the sealant 21 that seals the laminations 20, or it may be a different material. The encasement of the wire coils 25, 26 by the plastic 30 may be achieved by vacuum-pressure-heat molding as described and claimed in my copending application, Serial No. 286,880, filed May 9, 1952, in which the wound stator 11 is placed inside a suitable mold into which the plastic 30 is forced.

The sealant 21 or 30 may be the thermosetting plastic described and claimed in the application Serial No. 286,026 filed May 3, 1952, by myself, William Hodges and Tibor Wiener. This plastic is a filled epoxy-type polymer or epon resin having substantially the same coeflicient of thermal expansion as the iron laminations, so that there will be no breaking away by the resin. The preferred fillers are fine fiber asbestos and whiting. When properly applied, the plastic will not check, crack, or break away from the metal, but will act to make the stator 11 into a bonded unit not subject to leakage of gases therethrough even under high pressures. This plastic is not attacked by or dissolved by refrigerant fluids or most other fluids, so that it protects the wires.

The filling of the space between the wires 25, 26 with the plastic 36 aids in dissipating the heat that is generated in the wires. This solid fill of plastic, surrounding the wire bundles and each individual wire in the bundle, totally fills all the slot voids and provides a solid unbroken thermal path along which the wire heat is passed directly to the stator iron stack. This solid plastic fill is an appreciably better conductor of heat than air or vapor.

Preferably, there is no plastic film coating on the outer periphery 31 of the stator laminations 20, because any such film would tend to retard the heat dissipation from the motor-pump 10. Since no shell encloses the stator 11, the wire heat and stator stack heat are transferred directly to the surrounding air, which is in direct contact with the outer surface 31 of the laminations. If desired, for other reasons (e. g, for preventing corrosion in certain uses) the outer surface 31 and inner surface 22 may be electroplated or otherwise protected.

Another noteworthy feature of the stator 11 is the electrical fitting 32 shown in Figs. 1 and 10. Preferably, the fitting 32 consists of an electrically nonconductive circular flat disc 33 carrying three metallic female prong sockets 34. This electrical fitting 32 is partially encased in and sealed by the encasing material 30, so that there can be no leakage out from the pressure vessel along the wires. Preferably, the flat exterior surface 35 of the disc 33 is substantially fiush with the outer surface 36 of the stator coil encasing plastic 30. The terminals of stator wires 25, 26 are soldered to the inner-end of the sockets 34, and the sockets 34 are adapted to receive suitable companion male fittings (not shown) in the usual manner commonly associated with three-socket plugs.

The ends plates 12 and 13 In addition to the stator 11, the pressure vessel for the motor-pump comprises the pair of end plates 12 and 13 which close the ends of the stator cavity 14. The end plates 12 and 13 are in some manner ported to provide for the fluid intake and discharge openings. Figs. 1, 2, and 5 show the intake port 16 in the end plate 12. Figs. 2 and 7 show the discharge port 17 in the other end plate 13. However, as illustrated in Fig 9, both the intake and discharge ports may be in one end plate or may be in both end plates.

In their general shape, the end plates 12 and 13 are substantially identical. Two forms of end plates 12 and 13 are illustrated in Figs. 58. Figs. 5 and 6 show an end plate 12 adapted to be removably sealed to the stator 11 by a gasket means, whereas Figs. 7 and 8 show an end plate 13 adapted to be permanently sealed to the stator 11 by some sealant such as the plastic 30. It will be understood that normally both end plates 12 and 13 of anyone motor-pump 10 will be sealed in the same manner, either by gaskets or by a permanent sealant.

Both end plates 12 and 13 consist basically of a stepped disc 44 having a wider diameter outer portion 41 and a narrower-diameter axially-offset portion 42. The outer portion 41 has a generally smooth outer rim 43 which nests into the stator bore 22. A suitable O-ring 44 may lit in an outer annular groove 45 in the rim 43 to make the gasket connection with the stator bore 22.

The inner disc portion 42 preferably terminates in a flat wall 46, which is preferably ground to insure that it has a perfectly plane surface. The periphery 47 of the portion 42 is concentric with the outer rim 43 and forms a bearing surface for rotatably supporting the motor-rotor 15. The proportioning, spacing, and concentricity of the two peripheries 43 and 47 insure perfectly accurate alignment and spacing of the stator 11 and rotor 15 so that the clearance area 23 between them can be very small (ill 6 and so that uniform rotor-to-stator clearance and uniform rotor-to-stator parallelism are thereby assured. The inner edge of the bearing 47 may be chamfered at 48 to facilitate assembly of the parts, and a helical oil groove 49 may be provided around the bearing 47.

The end plates 12 and 13 may also be provided with an eccentricaly located, stepped circular opening 50 whose center C2 is radially offset with respect to the center C1 of the rim 43 and the bearing surface 47. The inner smaller-diameter portion 51 of the opening 50 engages the cylindrical body of a through-bolt 52 which extends beyond the shoulder 53 into the wider-diameter portion 54 of the opening 50. Blind nuts 55 may be threaded on the outer ends 56 of the bolt 52 so that they abut the shoulders 53 and thereby urge the end plates 12 and 13 inwardly against a cylindrical bearing member 83 which will be described later. Each blind nut 55 may be provided with an annular groove 56a in its outer surface to receive an O-ring 57 which makes a tight seal with the wall 58 of the opening 54. Or a portion 59 of the outer periphery of the blind nut 55 may be relieved and a sealant 59a forced therein to bond the nut 55 to the wall 58. For the sake of appearance covers 61) may be fitted flush into the counterbored opening 54.

The end plate 13 shown in Figs. 7 and 8 is identical with the end plate 12 except for the discharge opening 17, some oil grooves and bores (not described herein but referred to in my application Serial No. 292,140), and the means by which it is sealed to the stator 11. Instead of having a gasket type of seal, a portion 61 of the outer rim 43 is relieved to provide a space where plastic or other sealant 61a can be poured to bond the plate 13 to the stator bore 22. Normally, either both end plates 12, 13 will be sealed in this manner or both of them will have gaskets, but if desirable, one may be of one type and one of the other, as shown in Fig. 2.

The end plate 62 shown in Fig. 9 is like the end plates 12 and 13, except that it has both an intake port 63 and a discharge port 64. The opposite end plate may have no ports in it or may also have an intake and/ or a discharge port.

All of the intake and discharge ports 16, 17, 63, 64 may be threaded or otherwise adapted to receive the ends of suitable conduits therein.

Attachment of the end plates 12, 13 to a base 65 The motor-pump 16 may be used without a base, simply being supported by suitable brackets (not shown) afilxed to the stator 11. However, for some purposes, a base 65 is wanted, and then the supporting structure shown in Fig. 1 is preferred. In this event, a pair of counterbored threaded blind openings 66 are provided in each end plate 12, 13 (see Figs. 6 and 8). The vibration mount 67 may comprise a pair of flat head bolts 68, 69 having a resilient (e. g. rubber) portion 76 between them. The bolts 63 may be threaded into the end plate openings 66, and the bolts 69 may be bolted to the base 65 as shown in Fig. l. The isolation of the two bolts 68, 69 by the resilient separating body 70 serves to damp the vibrations of the motor-pump 10.

The motor-rotor 15 and the pump elements The motor-rotor 15 (see Figs. 2, 3, and 4) may be of the usual squirrel-cage induction design having generally annular projecting portions at each end.

Annular bearings 76 may be provided on the inner surface of the central rotor bore 77. The bearings 76 ride on the bearings 47 of the end plates.

An outer cylindrical pump element 78 may be press fitted or otherwise secured into the rotor bore 77 so that it becomes essentially integral with the rotor 15. In the drawings a hollow gear type of pump element '78 is shown with a toothed inner surface 79.

The inner gear element 80 may comprise a hollow cylindrical member having a toothed outer surface 81 driven by the toothed inner surface 79 of the outer element 78.

Preferably, the inner and outer gear elements 78 and 80 are of the so-called Rotoid type; that is, they have an odd number of teeth, and the outer element has two more teeth than the inner element. The teeth are preferably so constructed that there is a sliding contact between the inner and outer elements which is not broken over a considerable are as the gears rotate. Elements of this type are described and claimed in Patent No. 2,547,- 392, issued April 3, 1951, to Myron P. Hill and Francis A. Hill 2nd.

Preferably, the inner gear 80 is not concentric with the outer gear 78. The outer gear 78, being secured to the rotor 15, rotates about center C1, while the inner gear 80 rotates around the center C2. The inner gear bore 82 fits around a hollow cylindrical bearing 83 which, in turn, fits around the bolt 52.

The hollow cylindrical bearing 83 also acts as a stop and accurately spaces apart the end plates 12 and 13, the nuts 55 being tightened on the bolt 52 until the fiat surfaces 46 of both end plates 12, 13 are in tight contact with the radial faces 84 and 85 of the bearing 83, thereby placing the bearing 83 in compression.

The radial end faces of the gears 78, 81) are spaced apart from the end plate surfaces 46 enough to provide a running clearance. For this purpose, they are made almost, but not quite, as long as the bearing 83. A clearance of 0.0003 inch at each end has been used successfully.

Other types of pump elements may be used, as has been stated earlier, but a positive-displacement type of pump like the one illustrated in the drawings and further described and claimed in co-pending application, Serial No. 292,140, is preferable.

Assembly of the motor-pump 10 One blind nut 55 may be threadably attached to one end 56 of the through-bolt 52 and the bolt 52 may then be passed through the opening 50 in one end plate 12. The hollow cylindrical bearing 83 may be placed around the through-bolt 52 and the inner gear 80 placed around the bearing 83. The rotor 15, with the outer gear 78 secured to it, may then be placed over the inner gear 80, the motor-rotor bearings 76 being set to fully engage the bearing surface 47 on the end plate 12. The other end plate 1'3 may then be placed over the projecting bolt 52 and guided by the bolt until its bearing 47 is in full engagement with the motor-rotor bearings 76. The other blind nut 55 may then be threaded on its bolt end 56 and drawn up with sufficient tension to achieve slight compression of the hollow cylindrical spacer bearing 83 between the end plate inner faces 46, thereby completing assembly of a pump package. This pump package may then be placed within the stator bore 22. Depending on the type of end plates employed, the O-rings 44 and 57 will complete the seal of the pressure vessel, or a sealant 59a, 6111 will be poured in the reliefs 59 and 61 to bond the end plates 12 and 13 to the stator 11 and the blind nuts 55 to the end plates.

Operation When an electric current is applied to the windings 25, 26 of the stator 11, the rotor 15 will rotate on its bearings 47, 76. The outer pump element 78, being rigidly mounted to the rotor 15 will then drive the inner pump element 80, and fluid will be drawn in through the intake opening 16 and expelled through the discharge opening 17.

The sealants 21 and protect the wires 25, 26 from the fluid and also make the stator 11 pressure-tight. The blind nuts 55 are either gasketed or bonded to the end plates and the gasketing or bonding of the end plates 12, 13 to the stator 11 completes the fluid-tight pressure vessel for the motor-pump or compressor 10.

The heat generated inside the motor-pump 10 is dissipated out the outer periphery 31 of the laminations 20,

12, 13 so that the end plates are pressure-tight,

8 some of the heat being transmitted through the metal parts and some through the sealant 21, 30.

A motor-pump made substantially as shown and described hereinwithout any outer shellhas already run more than 800 hours under pressure without leakage, loss of charge, or pressure drop, and without any excessive heating. The stator and end plates constituted the pressure vessel, yet there Was no foreign coating in the air gap or on the outer periphery, all the sealing being done as described herein.

1 claim:

1. A motor-pump, including a hollow, laminated, wirebound stator, the laminations being bonded and sealed to each other by an impermeable plastic, the wires also being bonded and sealed to each other and to said laminations by said plastic, the bore and outer periphery of said stator laminations being uncoated by said plastic to expose bare metal there so that the rotor-to-stator clearance will be unaffected by said plastic and so that exterior air can freely carry away heat from the exterior of said stator laminations; a pair of stationary end plates sealed to said stator and forming therewith a gas-and-liquidtight pres sure vessel, each end plate being stepped and having its larger outer surface circular and fitting snugly in said stator bore and having its smaller inner surface circular and concentric with its outer surface, so as to form a hearing surface, one of said plates being provided with an intake port and said other plate being provided with a discharge port; a hollow motor rotor rotatably supported by said inner bearing surface and thereby properly spaced from said stator; and pump means inside said rotor for moving a fluid between said intake and discharge ports; said pump means including an inner element and an outer element, the outer pump-element being rigidly secured to said rotor inside said rotor.

2. The motor-pump of claim 1 in which there is an electric female plug containing a plurality of sockets electrically connected to terminals of said stator wires encased in and bonded to said plastic substantially flush therewith, whereby escape of fluid along said stator wires is prevented.

3. The motor pump of claim 1 in which said end plates have off-center openings therethrough, bolt means extending between said end plates and extending through said openings, and means securing said bolt means to said end plates.

4. The motor-pump of claim 3 in which the means for securing said bolts to said end plates comprises a pair of blind nuts, a shoulder in each of said bolt openings, and means for providing a fluid-tight seal between said blind nuts and said end plates.

5. The motor-pump of claim 4 in which said sealing means comprises an O-ring set in a groove in the outer surface of said blind nuts.

6. The motor-pump of claim 4 in which said sealing means comprises a sealant material bonded to said blind nuts and to said end plates.

7. The motor-pump of claim 3 in which there is a cylindrical stationary bearing member around said bolt between said end plates and abutting the inner surfaces of said end plates, said bearing member being under compression between said end plates, the inner gear element being rotatably mounted on said bearing member.

8. A motor-pump, including in combination a hollow, laminated, wire-wound stator, the laminations being bonded and sealed to each other by an impermeable plastic comprising an epoxy-type resin filled with asbestos fiber and whiting, the wires also being bonded and sealed to each other and to said laminations by said plastic, the bore and outer periphery of said stator laminations being uncoated by said plastic to expose bare metal there so that the rotor-to-stator clearance will be unaffected by said plastic and so that air can freely carry away heat from the exterior of said stator laminations; and electric female plug containing a plurality of sockets electrically con nected to terminals of said stator wires encased in and bonded to said plastic substantially flush therewith, whereby escape of fluid along said stator wires is prevented; a pair of stationary end plates each comprising a stepped disc sealed to said stator inside the bore of said stator and forming with said stator a pressure vessel, the outer circular surface of larger diameter fitting snugly in said stator bore and sealed thereto, said end plates each having an axially olfset portion projecting into said bore with an outer bearing surface of smaller diameter than and coaxial with said larger diameter surface, one of said plates being provided with an intake port and said other plate being provided with a discharge port, said end plates having off-center openings therethrough; bolt means extending between said end plates and extending through said openings, blind nuts securing said bolt means to said end plates, said nuts being sealed to said end plates; a hollow motor rotor rotatably supported by said projecting bearing and thereby properly spaced from and angularly aligned with said stator; pump means inside said rotor for moving a fluid between said intake and discharge ports; said pump means including an inner element and an outer element; the outer pump element being rigidly secured to said rotor inside said rotor; and a cylindrical stationary, bearing member around said bolt between said end plates and abutting the inner surfaces of said end plates, said bearing member being under compression between said end plates, said inner gear element being rotatably mounted on said bearing member.

9. An electric motor pump, including in combination a hollow, laminated, wire-wound stator, with its laminations and wires bonded and sealed together by thermosetting impermeable plastic in a fluid-tight seal, the bore being uncoated by said plastic to expose bare metal; a pair of stationary end plates sealed to said stator and forming therewith a gas-and-liquid tight pressure vessel, each end plate being stepped and having its larger outer surface circular and fitting snugly in said stator bore and having its smaller inner surface circular and concentric with its outer surface so as to form a bearing surface, at least one of said plates being ported so that said motor pump has intake and discharge means; a hollow motor rotor rotatably supported by said bearing surface and thereby spaced from said stator; and pump means inside said rotor for moving a fluid between said intake and discharge means, said pump having an inner element and an outer element, the outer pump element being rigidly secured to said rotor inside said rotor.

10. The motor-pump of claim 9 in which there is an electric female plug containing a plurality of sockets electrically connected to terminals of the stator wires and encased in and bonded to said plastic substantially flush therewith, whereby escape of fluid along said stator wires is prevented.

11. An electric motor pump, including in combination a fluid-impervious stator having a bore therethrough; a pair of stationary end plates sealed to said stator and forming therewith a gas-and-liquid tight pressure vessel, each end plate being stepped and having its larger outer surface circular and fitting snugly in said stator bore and having its smaller inner surface circular and concentric with its outer surface so as to form a bearing surface, at least one of said plates being ported so that said motor pump has intake and discharge means; a hollow motor rotor rotatably supported by said bearing surface and thereby spaced from said stator; and pump means inside said rotor for moving a fluid between said intake and discharge means, said pump having an inner element and an outer element, the outer pump element being rigidly secured to said rotor inside said rotor.

12. An electric motor-pump, including in combination a fluid-impervious stator having a bore therethrough; a pair of stationary end plates sealed to said stator and forming therewith a gas-and-liquid tight pressure vessel, each end plate having two concentric circular surfaces, a larger outer surface fitting snugly in said stator bore and and a smaller inner bearing surface, at least one of said plates being ported so that said motor pump has intake and discharge means; a hollow motor rotor rotatably supported by said bearing surface and thereby spaced from said stator; and pump means inside said rotor for moving a fluid between said intake and discharge means, said pump having an inner element and an outer element, the outer pump element being rigidly secured to said rotor inside said rotor.

13. The motor-pump of claim 12 in which said end plates have aligned off-center openings therethrough, bolt means extending between said end plates and extending through said openings, and means securing said bolt means to said end plates.

14. The motor-pump of claim 13 in which the means securing said bolt means to said end plates comprises a pair of blind nuts, a shoulder in each of said off-center openings, and means for providing a fluid-tight seal between sa'id blind nuts and said end plates.

15. The motor-pump of claim 14 in which said means for providing a fluid-tight seal comprises an O-ring set in a groove in the outer surface of said blind nuts.

16. The motor-pump of claim 14 in which said means for providing a fluid-tight seal comprises a sealant material bonded to said blind nuts and to said end plates.

17. The motor-pump of claim 13 in which there is a cylindrical stationary bearing member around said bolt means between said end plates and abutting the inner surfaces of said end plates, said bearing member being under compression between said end plates, the inner pump element being rotatably mounted on said bearing member.

References Cited in the file of this patent UNITED STATES PATENTS 1,440,952 Apple Jan. 2, 1923 1,449,371 Apple Mar. 27, 1923 1,759,766 Szmukler May 20, 1930 1,780,337 Canton Nov. 4, 1930 1,780,338 Canton Nov. 4, 1930 1,780,339 Canton Nov. 4, 1930 1,849,222 Canton Mar. 15, 1932 1,881,344 Apple Oct. 4, 1932 1,911,128 Apple May 23, 1933 2,057,503 Sawyer Oct. 13, 1936 2,140,966 Nichols Dec. 20, 1938 2,161,374 Moineau June 6, 1939 2,246,275 Davidson June 17, 1941 2,263,515 Pezzillo Nov. 18, 1941 2,274,274 Pezzillo Feb. 24, 1942 2,285,050 Pezzillo June 2, 1942 2,312,848 Pezzillo Mar. 2, 1943 2,319,730 Garraway May 18, 1943 2,419,159 Pezzillo Apr. 15, 1947 2,420,124 Coulson May 6, 1947 2,423,345 Roters July 1, 1947 2,494,295 Greenless Ian. 10, 1950 2,500,600 Bradley Mar. 14, 1950 2,579,865 Roters Dec. 25, 1951 OTHER REFERENCES Ethoxylines by Preiswerk and Meyerhans, Electrical Manufacturing, July 1949, pp. 78-81, 164, 166. 

